Molded chair shells have been well known in the art for some time. A typical example of a molded chair shell is disclosed in U.S. Pat. No. 3,669,496, which includes a single, molded piece that forms the seat and the seat back. The chair further requires a frame, i.e., a back support, to which the molded piece is attached. Another example of a molded chair is disclosed in U.S. Pat. No. 3,751,109, which shows a single, molded piece with legs attached at the bottom. This chair does not have a back support and therefore may be prone to material failure.
U.S. Pat. No. 5,985,188 discloses a method and mold design for forming a molded chair seat portion and chair back support portion using air counter pressure and two different materials in an injection molding procedure. The two different materials comprise a first material having a low flexural modulus and the other material having a high flexural modulus. Other additives for tailoring the physical properties of the molded product are added to the mixture of the two materials. The air counter pressure is achieved using shop air pressure. The mold may be used to form the seat portion and the back support portion with a single stroke. An endothermic foaming or blowing agent is added to the mixture of the two materials to reduce the weight of the finished part, to reduce cycle time, and to assist in the uniform distribution of the materials that are injected into the mold cavity by the injection nozzle.
U.S. Pat. No. 7,600,820 discloses a molded chair shell which includes a seat portion and a back portion joined at a junction area. A support or reinforcement member is located at the junction area and is formed integrally with the seat portion and the back portion. The reinforcement member includes an internal cavity between the seat portion and the back portion that is substantially positioned over the junction area. The cavity is formed by cavity walls, which may form ribs that extend forwardly along the seat portion and upwardly along the back portion of the chair shell. The chair shell may be formed in an injection molding process, and the internal cavity may be formed in a gas assist operation carried out during the injection molding process.
While these molded chairs have been useful, there is a need for a molded chair which is aesthetically pleasing and which provides for increased strength and reduced weight compared to traditional plastic chairs formed with known methods.